Elbow connection for use with spark plugs



1945- B. w. HULFISH,

ELBOW CONNECTIbN FOR USE WITH SPARK PLUGS Filed Oct. 6, 1943 2 Sheqts-Sheeg l IIIII IIIIIIIIIWIA .ELBOW CONNECTION FOR USE WITH SPARK PLUGS Filed Oct. 6, 1943 2 Sheets-Sheet 2 awucwho'n Patented Aug. 7, 1945 s OFFICE Appetite OctoberG,

1943, seem 505,256

2Claims. (o1; iri -35) This invention relatestoimprovementS- in elbowconnections-for uselwith spark plugs and more particularly'to. an elbow-joint especially adapted for usewith-zthe spark plugs of aircraft. I

The;present war has developed mass production of'aircraft engineswith the result that-such enginesall usevv radio .shieldedspark plugs, which are identicalin physical size,' shape;-and connection detail. They e-ialso employ identical spark. plug elbows which-n consist: of v a casing onlybthrough which thei-ignition lead with its insulation. runsv unbrokento-ithe spark plug. These elbows, however; are produced with different angularbends. .They, alsoyuse connector assemblies, consisting:chaninsulative sleeve, a ferrule, and a spring,..which serve to secure the end of .the ignitionleadwat. the spark plug: and make electric connection, and provide a long flash-over distance to grounded metallic radio shielding members. Sparkap1ugs,=elbows, and connector .assemblies atzthe present time are made in huge quantities, and their physical shape and size have become practically -standard for thepresentand near future. H

Many failures of lead insulation occur-in present elbows, or between elbows and spark plugs. They are due to heat and'the-reduction of the dielectric strength of the rubber insulation when in tension, as itis -in the outer portion of the bend through the elbow. "Also, the failures are sometimes due to moisture entering at-the connection of the'elbow casing; 'In still other cases, faults are due toithe failure of the seal around the internal insulation of the spark plug, whichallows oil and gas froin the engine cylinder to pass into the elbow and along. the lead conductor under the insulation covering, with detrimental effect.

' The primarypurposes ofthe'present inveri tion is to provide a novel elbow connection designed to eliminate suchdefects. I g Another object is to: supply an elbow which may be installedin place'o f the hollow elbow now in use,'without the necessity of shortening the flexible radio shielding of the ignition lead extendingfrom the elbow to the ignition .manifold. This feature provides advantages; first, the elbow may be applied. to ignition harness'es made for existin g hollowv elbows with-a minimum of labor and withoutcertain tools and. equipment for shorteningthe flexible shielding, and second, the elbows can be,.used to-replace. hollow elbows; ens zengines which.are: in

service whentfacilitiestfor shortening the flexible shielding are not available.

.Another objectis to furnish an elbow with built-ininsulating material whichv adheres so tightly: totheconductor assembly that a. seal iscreatedagainstzthe passage of-liquid or gas, from an internally=leaking..spark plug, to the cavityprovided for:- the ignition lead connection, hence,i,along the conductor of the. lead under its insulation.

A still: further object is to provide an elbow having .a seal against entrance of liquid. or gas wherethe elbow casing-.engagesthe top edge of the spark plugshielding, accomplished by arranging additional insulation material along the aneavof contact with the plug edge.

A; stillzfurther object is to supply an: elbow havingaseal againstentrance. of liquldor gas where the-elbow casing engages the end of the flexible lead-shielding, which isachievedby extending-the insulating. material slightly beyond an end of the-elbow casing soxthat it .will' engage part" of the end of the shielding, all the. way around. v

A further object is to provide an elbow in which my. improvements are incorporated and having a cavity to accommodate the ignition lead connection so that it :will take the connector assembly now in common: use;

,A. still further object is toaproducera. simple and practical elbow connection and yet one which will be. exceedinglyefiectivefor the purposes f or which it'isdesigned.

, With the foregoing .objects outlined and with other objects in view which-will appear'as the description proceeds, the invention consists in thei-inovelfeatures hereinafter described in detail, illustratedainthe accompanying drawings, and. more particularly pointedqout in the app nded claims.

Referring to the drawings: Fig; l is a side: elevation. of .my improved elbow assembly. I i 1 Fig. 2iis an enlarged longitudinal vertical sectional view 'of the same.

Fig. 3 is another side elevationtaken' at right angles toFig..1 and'with the nut :oi the assembly not shown.

I Fig. 4 is alongitudinal sectional view of a modification of the elbowzassembly shown connected to: a spark plug. and-- ignition harness,

lnthe embodiment of theinvention illustrated .in. Figs.. 1 to 3, inclusive-'5'designatesan elbow shaped casing formed of anysuitableconducting material, .such as metal, .and having upper 2 L11 arm 6 provided with external screw threads 1. The casing, also, includes a leg 8 terminated in a flared mouth or flange 9.

In the manufacture of my elbow assembly, I mold suitable insulating material H), such as synthetic rubber, within the casing, and before doing sum n ge a.-,conductor.assembly H partly within tea-.1 This assembly comprises a threaded stud I2 to which is connected a conductor I3 small enough in diameter to permit it to bend after the assembly of the elbow is completed. I prefer to use a. conductor of a diameter of about 3 2" instead of the conventional conductors which are about in diameter. The conductor is secured at itsupper end to a conductor disk l5 provided with a blind hole I53;

and a threaded aperture I6 for a purpose hereinafter disclosed. To facilitate manufacture, the internal conductor assembly is secured at the threaded end l2 and, also, near the opposite end bymeans of a threaded stud, not shown, which engages the threads of the aperture l6 while the insulating material which is in plastic condition is being injection-molded into the casing. This assures that the conductor assembly will be positioned as desired. In the-molding an extension I! is formed below the casing.

This extension either during the molding or afterwards is positioned within a ceramic sleeve I8 that has a recess is at its lower end for the accommodation of a nut 20 which engages the threaded end of the conductor assembly to secure the sleeve in place, and, also, serves as anchoring means for the upper end of a conductor spring'2l. Durin the molding, the insulation is provided with a circular bead 22 which fills the-flared mouth 9. Also, during the molding, a plug (not shown) having a dowel pin to fit projects beyond the end of the arm 6.

The assembly is completed by a nut 25 which cooperates with the flange 9 in securing the elbow to the casing of the spark plug. It will be noted that the nut due to theshape and length of the off the flange 9 to facilitate inspection of the joint.

In Fig. 4 the construction of the elbow assembly is the same as the one illustrated in Fig. 3 with the exception that the leg 8a projects at a diiTerent angle from the arm 6a. In Fig. 4. the end portion 26 of the ignition harness 21 is shown extending into the elbow assembly with its spring 28. contacting the disk l5a. Furthermore, in this view, the nut 29 of the harness is shown clamping the end 30 of the flexible radio shielding of the harness against anend of the casing I'he synthetic rubber which I propose to use as insulation in the elbow assembly is somewhat flexible in its. final cured state. Thus, by providing. a flexible conductor l3 embedded in the synthetic rubber, the portion of the assembly :which projects beyond the casing of the elbow will not be rigid. Therefore, it can be bent away fromthe straight-axis of the leg of the elbow. Thisfeature of the assembly will greatly-facilistraight line, and be availableor stretching occurs in the ignition being replaced in tate the installation and removal of the elbow from the spark plug in cases where there may be other adjacent engine parts which provide interference. It will, also, be an advantage in the case of a elbow.

Other advantages of the use of the smaller diameter conductor l3 are: .less heatconducted into the insulation and the connection cavity 22; greater thickness of insulation between the conductor and casing, and somewhat smaller condenser value for the elbow.

Economical and effective use is made of the insulating material within the elbow by providing less thickness where other insulation already exists, and by providing greater thickness of insulation where no other insulation exists, that is, between the outer metallic casing and the internal conductor I3. Accordingly, the insulation is thinner around the cavity 23 toward the open end where insulation is present on the ignition lead itself, and is thicker around that portion of the cavity that will contain the uninsulated spring contact 28 on the end of the connector assembly.

Disconnectionof the ignition lead from the elbow is obtained simply by unscrewing the nut .29 which secures the flexible shielding to the casing of the elbow. Therefore, the ignition lead may be disconnected from the elbow, without previously removing the elbow from the spark plug. This is advantageous especially in the case of the 70 elbow which cannot be removed from the spark plug when the ignition lead is attached unless sufficient slack or additional length is provided in the ignition lead. The shorter the length of the flexible ignition lead from the elbow to the ignition manifold (not shown), the more serious the task of removing the elbow becomes without disconnecting the ignition lead at the elbow. The condition arises from the fact that the connection end 01' the elbow heretofore used and which extends into the spark plug is rigid, and, therefore, must be withdrawn from the spark plug along a to achieve this path, slack must lead beyond the nected.

As hereinbefore mentioned, the nut 25, 250 may be unscrewed from the spark plug and moved back to a position where the contact between the elbow casing and the spark plug shielding can be viewed. This i desirable for inspection purposes, and particularly in cases when the voids, remaining, in the spark plug cavity after insertion of the connection end of the elbow, are to be filled with an insulation fluid compound. Such an expedient is frequently used and inspection is required to see that the voids have been filled and that no excess compound exists at the joint to impair the making of metal to metal contact between the spark plug and elbow casings.

The only spring 2|, 2|a in the elbow assembly is removable and replaceable with the nut (20). This saves an elbow assembly from being discarded when a spring loses its temper or becomes broken.

The ceramic sleeve insulation I8 which goes into the spark plug cavity is, also, capable of case of damage to a sleeve.

As the contact disks l5, I5a have rounded edges, they are much better in high frequency and high voltage construction than disks having elbow unless it can be disconsquare edges.

From the foregoing, it is believed that the construction and advantages of my elbow assembly will be clearly understood without further description, and it will, also, be understood that the embodiments of my invention herein disclosed are to be taken as examples only as the invention may be embodied in other constructions falling within the terms of the appended claims.

What I claim and desire to secure by Letters Patent is:

1. An elbow assembly for use with a shielded spark plug, comprising an elbow shaped casing having an arm and a leg, flexible insulating material filling said leg and lining said arm, said insulating material forming a substantially cylindrical flexible projection depending from said leg, at contact element positioned in the casing and insulated by said material, a flexible conductor extending from said element and embedded in the insulating material in said leg 20 and projection, a stud connected to the flexible conductor and extending beyond said projection,

and a sleeve of rigid insulating material surrounding said projection, spaced from said legand removably secured to said threaded stud.

2. An elbow assembly for use with a shielded spark plug, comprising an elbow shaped casing of conducting material having an arm and a leg, flexible insulating material molded within the casing, filling the said leg and lining said arm, said insulating material forming a substantially cylindrical projection depending from said leg, a contact element positioned in the casing at the inner end of the lining, a flexible conductor extending from said element and embedded in said insulating material and said projection, a threaded stud connected to the flexible conductor and extending beyond said projection, a rigid sleeve of insulating material surrounding said projection, a nut having threaded engagement with the stud and removably securing the sleeve in position, and a contact element projecting from said nut.

' BUFORD WAGONER HULFISH. 

